Disposable Absorbent Articles

ABSTRACT

An absorbent article including an absorbent core having a fluid distribution layer and fluid storage layer, the fluid distribution layer being formed of two or more sub-layers. A first sub-layer has a first amount of multiple component binder fibers or crosslinked cellulose fibers, or a combination thereof. A second and/or subsequent sub-layer comprises treated or untreated pulp and a second amount of multiple component binder fibers, crosslinked cellulose fibers, or a combination thereof. The % by weight of the first sub-layer of the first amount of multicomponent binder fibers and/or crosslinked cellulose fibers is greater than the % by weight of the second or subsequent sub-layer of the second amount of multiple component binder fibers and/or crosslinked cellulose fibers.

FIELD OF THE INVENTION

The present disclosure generally relates to a disposable absorbentarticle having an absorbent core comprising a fluid distribution layerand a fluid storage layer.

BACKGROUND OF THE INVENTION

Disposable absorbent articles such as feminine hygiene products, tapeddiapers, pant-type diapers and incontinence products are designed toabsorb fluids from the wearer's body. Users of such disposable absorbentarticles have several concerns. Leakage from products like catamenialpads, diapers, sanitary napkins, and incontinence pads is a significantconcern. Comfort and the feel of the product against the wearer's bodyis also a concern. To provide better comfort, current disposablearticles are typically provided with a topsheet that is flexible, softfeeling, and non-irritating to the wearer's skin. The topsheet does notitself hold the discharged fluid. Instead, the topsheet isfluid-permeable to allow the fluids to flow into an absorbent core.

Current disposable articles are also provided with an absorbent core,also referred to as an absorbent system, typically comprising anacquisition and/or fluid distribution layer and a fluid storage layer.The fluid distribution layer is typically placed on top of the bodyfacing surface of the fluid storage layer and has the function ofrapidly acquiring fluids excreted from the body and transferring themrapidly away from the body into the fluid storage layer. The fluiddistribution layer is also used to keep exudates held in the fluidstorage layer away from the skin surface during use and/or as pressureis applied to the article. This leads to a constant trade-off betweeneffectiveness of a fluid distribution layer to draw liquid away from thesurface, while still providing a comfortable and dry absorbent article.

The present invention seeks to further improve this trade-off betweencomfort and effectiveness in an absorbent article by providing aspecifically designed absorbent core to ensure effective absorptionwhile providing a more pleasant consumer experience.

SUMMARY OF THE INVENTION

The present invention relates to an absorbent article having a topsheet,backsheet and absorbent core. The absorbent core has a fluiddistribution layer, adjacent the topsheet and a fluid storage layerbetween the fluid distribution layer and the backsheet. The fluiddistribution layer is formed of two or more sub-layers, the firstsub-layer proximal to the topsheet having a first amount of multiplecomponent binder fibers or crosslinked cellulose fibers, or acombination thereof. A second and/or subsequent sub-layer distal fromthe topsheet comprises treated or untreated pulp and a second amount ofmultiple component binder fibers, crosslinked cellulose fibers, or acombination thereof The % by weight of the first sub-layer of the firstamount of multicomponent binder fibers and/or crosslinked cellulosefibers is greater than the % by weight of the second or subsequentsub-layer of the second amount of multiple component binder fibersand/or crosslinked cellulose fibers. Furthermore, the fluid storagelayer has at least 50% by weight of the fluid storage layer of a superabsorbent polymer.

The fluid distribution layer is configured to quickly acquire liquidfrom the topsheet, drawing it deep into the fluid distribution layeruntil such time that the liquid is absorbed by the fluid storage layer.By providing a greater % by weight of the layer of multicomponent binderfibers and/or crosslinked cellulose fibers in the first sub-layercompared with the second and/or subsequent layer provides a fluiddistribution layer with a relatively more open structure in an areaproximal to the topsheet. The open structure enables quick acquisitionof liquid from the top sheet and has good recovery properties afterliquid has been drawn down through the second sub-layer and into thefluid storage layer. The second and/or subsequent sub-layer balances theneed to draw liquid from the topsheet and to retain it until absorptionby the fluid storage layer, thereby preventing rewet during use of suchan absorbent article.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one example of an absorbent article thatincorporates an absorbent core.

FIGS. 2A and 2B are representative cross-sectional views of theabsorbent article of FIG. 1 taken through line 2-2.

FIGS. 3, 4A, 4B, 5A and 5B are schematic representations of theequipment used to measure Multiple Strike Through and End Rewet.

FIG. 6A shows the results of the Stain Size Test conducted on anexemplary topsheet.

FIG. 6B shows the results of the Stain Size Test conducted on anexemplary fluid distribution layer.

FIG. 6C shows the results of the Stain Size Test conducted on a controltopsheet and fluid distribution layer.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter that is regarded as thepresent invention, it is believed that the invention will be more fullyunderstood from the following description taken in conjunction with theaccompanying drawings. Some of the figures may have been simplified bythe omission of selected elements for the purpose of more clearlyshowing other elements. Such omissions of elements in some figures arenot necessarily indicative of the presence or absence of particularelements in any of the exemplary embodiments, except as may beexplicitly delineated in the corresponding written description. Thedrawings are not necessarily to scale.

DETAILED DESCRIPTION

As used herein, the following terms shall have the meaning specifiedthereafter:

All percentages are to be considered as weight percentages unlessotherwise specified.

“Absorbent article” refers to wearable devices, which absorb and/orcontain liquid, and more specifically, refers to devices, which areplaced against or in proximity to the body of the wearer to absorb andcontain the various exudates discharged from the body, such as menses orurine. Absorbent articles can include diapers, training pants, adultincontinence undergarments (e.g., liners, pads and briefs) and/orfeminine hygiene products.

The “longitudinal” direction is a direction running parallel to themaximum linear dimension, typically the longitudinal axis, of thearticle and includes directions within 45° of the longitudinaldirection. “Length” of the article or component thereof, when usedherein, generally refers to the size/distance of the maximum lineardimension, or typically to the size/distance of the longitudinal axis,of an article or part thereof.

The “lateral” or “transverse” direction is orthogonal to thelongitudinal direction, i.e., in the same plane as the majority of thearticle and the longitudinal axis, and the transverse direction isparallel to the transverse axis. “Width” of the article or of acomponent thereof, when used herein, refers to the size/distance of thedimension orthogonal to the longitudinal direction of the article orcomponent thereof, i.e., orthogonal to the length of the article orcomponent thereof, and typically it refers to the distance/size of thedimension parallel of the transverse axis of the article or component.

The “Z-direction”, or “thickness” is orthogonal to both the longitudinaland transverse directions and typically extends from the upperbody-facing surface of the absorbent article to the lower garment-facingsurface.

“Machine Direction” or “MD” as used herein means the direction parallelto the flow of a manufacturing machine, such as the airlaid makingmachine and/or absorbent article product manufacturing equipment.

“Cross Machine Direction” or “CD” as used herein means the directionparallel to the width of the manufacturing machine, for example anairlaid making machine and/or absorbent article product manufacturingequipment and perpendicular to the machine direction.

The terms “upper”, “upward” or corresponding expressions referz-directionally to a direction or relative orientation or positioning ofan absorbent article or its components when in use as positioned or wornby a user and relative to the user's body. Thus, a topsheet of anabsorbent article may be positioned as the most outward layer of thearticle and its outer surface may be intended for contact with the skinof a wearer. Accordingly, the absorbent article may exhibit “upper”elements or surfaces that are positioned relative to other “lower”elements or components that are positioned further away from a user'sskin during use.

Likewise, the terms “lower”, “downwards” or corresponding expressionsrefer z-directionally to a direction or relative orientation orpositioning of an absorbent article or its components when in use aspositioned or worn by a user and relative to the user's body. Typically,a backsheet of an absorbent article may be positioned as the outermostlayer of the article and its outer surface may be intended to be incontact with the garment of a wearer.

“Absorbent core” or “absorbent system” refers to a structure typicallydisposed between a topsheet and backsheet of an absorbent article forabsorbing and containing liquid received by the absorbent article. Inthe present invention, the absorbent core includes at least a fluiddistribution (or fluid acquisition) layer and fluid storage layer,however it will be appreciated that the absorbent core may include otherlayers that are positioned between the topsheet and backsheet.

As used herein, the term “foam” is synonymous with the term “cellularpolymer” which includes materials having a significant void volume,typically greater than 75%. “Open-celled” foams further have areticulated internal structure disposed therein comprising relativelythin “strut” elements interconnected and forming cells or poresproviding for fluid communication throughout the structure. Mean celldiameters refer to the diameter of the pores in the foam visible bymicroscopy. The pores tend to be relatively spherical in shape and themean diameter can be measured by using microscopic techniques. Onesuitable technique is to use a scanning electron micrograph and measurethe apparent mean diameter of at least 25 representative cells todetermine the mean. The density of foams can be determined usinguncompressed samples of said foams devoid of contaminants such as water,and measuring the volume and weight of the foam. A cubic sample havingan edge length greater than or equal to 2cm is practical.

In all cases, when describing the absorbent article and the absorbentcore of the present invention, it is considered that the article and theabsorbent structure are in a flattened configuration where the plane ofthe article is the x,y plane and the z axis is perpendicular to saidplane.

The term “treated pulp” is equivalent to “softener treated pulp” and to“debonder treated pulp”, all of which refer to fluff pulp treated withdebonding agents which reduce the strength of hydrogen bonding betweencellulose molecules.

“Nonwoven material” refers to a manufactured web of directionally orrandomly oriented fibers, excluding paper and products which are woven,knitted, tufted, stitch-bonded incorporating binding yarns or filaments,or felted by wet-milling, whether or not additionally needled. Nonwovenmaterials and processes for making them are known in the art. Generally,processes for making nonwoven materials comprise laying fibers onto aforming surface, which can comprise spunlaying, meltblowing, carding,airlaying, wetlaying, coform and combinations thereof. The fibers can beof natural or man-made origin and may be staple fibers or continuousfilaments or be formed in situ.

The term “hydrophilic” describes fibers or surfaces of fibers, which arewettable by aqueous fluids (e.g., aqueous body fluids) deposited onthese fibers. Hydrophilicity and wettability are typically defined interms of contact angle and the surface tension of fluids as they passthrough a material. A fiber or surface of a fiber is said to be wettedby an aqueous fluid (i.e., hydrophilic) when either the contact anglebetween the fluid and the fiber, or its surface, is less than 90degrees, or when the fluid tends to spread spontaneously across thesurface of the fiber. Conversely, a fiber or surface of the fiber isconsidered to be “hydrophobic” if the contact angle is greater than 90degrees and the fluid does not spread spontaneously across the surfaceof the fiber.

Absorbent Article

A disposable absorbent article as disclosed herein may take a variety ofdifferent forms, such as diapers, feminine hygiene products andincontinence products such as sanitary napkins and incontinence pads.One non-limiting embodiment of a disposable absorbent article asdetailed herein is shown as a sanitary napkin in FIGS. 1 and 2. For thepurposes of this application, a sanitary napkin will be specificallyillustrated and described, although any features or elements of thesanitary napkin that are disclosed are also contemplated for any otherembodiment of absorbent article, including incontinence pads.

A sanitary napkin 10 can have any shape known in the art for femininehygiene articles, including the generally symmetric “hourglass” shapeshown in FIG. 1, as well as pear shapes, ovals, oblong ovals, dropletshapes, bicycle-seat shapes, trapezoidal shapes, or wedge shapes.Sanitary napkins and pantiliners can also be provided with lateralextensions known in the art as “flaps” or “wings” (not shown in FIG. 1).Such extensions can serve a number of purposes, including, but notlimited to, protecting the wearer's panties from soiling and keeping thesanitary napkin secured in place. The illustrated absorbent article hasa body-facing upper side that contacts the user's body during use. Theopposite, garment-facing lower side contacts the user's clothing duringuse.

The upper side of the sanitary napkin 10 generally has a topsheet 14that can be liquid pervious. The lower side (seen in FIGS. 2A and 2B)has a backsheet 16 that is often liquid impervious and is joined withthe topsheet 14 at the edges of the sanitary napkin 10. The backsheetand the topsheet may be secured together in a variety of ways, forexample with adhesive, heat bonding, pressure bonding, ultrasonicbonding, dynamic mechanical bonding, a crimp seal, or by any othersuitable securing method. As shown in FIG. 2, a fluid impermeable crimpseal 24 can resist lateral migration (“wicking”) of fluid through theedges of the product, inhibiting side soiling of the wearer'sundergarments.

As is typical for sanitary napkins and the like, the sanitary napkin 10of the present disclosure can have panty-fastening adhesive disposed onthe garment-facing side of the backsheet 16. The panty-fasteningadhesive can be any of known adhesives used in the art for this purpose,and can be covered prior to use by a release paper, as is well known inthe art. If flaps or wings are present, a panty fastening adhesive canbe applied to the garment facing side so as to contact and adhere to theunderside of the wearer's panties.

An absorbent core 18 is positioned between the topsheet 14 and thebacksheet 16. The illustrated sanitary napkin 10 has a body-facing upperside 11 that contacts the user's body during use. The opposite,garment-facing lower side 13 contacts the user's clothing during use. Asshown in FIG. 2A, the absorbent core 18 may include a fluid distributionlayer 20 for drawing liquid into the sanitary napkin from the topsheetand a fluid storage layer 22 where exudates are eventually held.

The topsheet 14 and the backsheet 16 may be joined directly to eachother in the periphery of the sanitary napkin or they may be indirectlyjoined together by directly joining them to the absorbent core 18 oradditional optional layers within the chassis, such as a secondarytopsheet.

Topsheet

The absorbent article may comprise any known or otherwise effectivetopsheet, such as one which is compliant, soft feeling, andnon-irritating to the wearer's skin. Suitable topsheet materials includea liquid pervious material that is oriented towards and contacts thebody of the wearer permitting bodily discharges to rapidly penetratethrough it without allowing fluid to flow back through the topsheet tothe skin of the wearer. A suitable topsheet can be made of variousmaterials such as woven and nonwoven materials; aperture film materialsincluding aperture formed thermoplastic films, aperture plastic films,and fiber-entangled aperture films; hydro-formed thermoplastic films;porous foams; reticulated foams; reticulated thermoplastic films;thermoplastic scrims; or combinations thereof. Suitable woven andnonwoven materials can comprise natural fibers (e.g., wood or cottonfibers), synthetic fibers (e.g., polymeric fibers such as polyester,polypropylene, or polyethylene fibers) or from a combination of naturaland synthetic fibers. When the topsheet comprises a nonwoven web, theweb may be manufactured by a wide number of known techniques. Forexample, the web may be spunbonded, carded, wet-laid, melt-blown,hydroentangled, combinations of the above, or the like. Suitablenonwoven materials may include low basis weight nonwovens, that is,nonwovens having a basis weight of from about 8 g/m² to about 25 g/m².

Topsheets may be formed by one or more of the layers made of thematerials mentioned above, where one layer forms the outer surface ofthe absorbent article and one or more other layers are positionedimmediately below it. The layer forming the outer surface of the articleis typically a nonwoven layer or a formed film and it can be treated tobe hydrophilic using surfactants or other means known to the personskilled in the art. Topsheets may additionally be apertured, have anysuitable three-dimensional feature and/or have a plurality ofembossments (e.g., a bond pattern). The topsheet may additionally beprovided with tufts, formed with a laminated topsheet having anapertured upper layer and nonwoven lower layer, with “tufts” formed fromthe nonwoven layer protruding through the apertured upper layer.

Backsheet

The backsheet acts as a barrier to any absorbed bodily fluids that maypass through the absorbent core to the garment surface thereof with aresulting reduction in risk of staining undergarments or other clothing.Further, the barrier properties of the backsheet permit manual removal,if a wearer so desires, of the absorbent article with reduced risk ofhand soiling. The backsheet may be positioned adjacent a garment-facingsurface of the absorbent core and may be joined thereto by attachmentmethods (not shown) such as those well known in the art. For example,the backsheet may be secured to the absorbent core by a uniformcontinuous layer of adhesive, a patterned layer of adhesive, or an arrayof separate lines, spirals, or spots of adhesive. Alternatively, theattachment methods may comprise using heat bonds, pressure bonds,ultrasonic bonds, dynamic mechanical bonds, or any other suitableattachment methods or combinations of attachment methods. Forms of thepresent disclosure are also contemplated wherein the absorbent core isnot joined to the backsheet, the topsheet or both.

The backsheet may be impervious, or substantially impervious, to liquids(e.g., menses or urine) and may be manufactured from a thin plasticfilm, although other flexible liquid impervious materials may also beused. As used herein, the term “flexible” refers to materials which arecompliant and will readily conform to the general shape and contours ofthe human body. The backsheet may prevent, or at least inhibit, theexudates absorbed and contained in the absorbent core from wettingarticles of clothing which contact the absorbent article such asundergarments. However, in some instances, the backsheet may permitvapors to escape from the absorbent core (i.e., it is breathable) whilein other instances the backsheet may not permit vapors to escape (i.e.,non-breathable). Thus, the backsheet may comprise a polymeric film suchas thermoplastic films of polyethylene or polypropylene. A suitablematerial for the backsheet is a thermoplastic film having a thickness offrom about 0.012 mm to about 0.051 mm, for example.

Another suitable backsheet material is a polyethylene film having athickness of from about 0.012 mm to about 0.051 mm. The backsheet may beembossed and/or matte finished to provide a more clothlike appearance.For a stretchable but non-elastic breathable (i.e., permeable to watervapour and other gases) backsheet, a hydrophobic, stretchable, spunlaced, non-woven material having a basis weight of from about 30 g/m² to40 g/m², formed of polyethylene terephthalate or polypropylene fibersmay be used. Other suitable breathable backsheets for use herein includesingle layer breathable backsheets which may be breathable and liquidimpervious, and backsheets formed of two or more layers which incombination provide breathability and liquid imperviousness. Forexample, the backsheet may have a first layer comprising a gas permeableaperture formed film layer and a second layer comprising a breathablemicroporous film layer.

Where the backsheet is formed of a nonwoven web, it may have a basisweight of between 20 g/m² and 50 g/m².

Absorbent Core

Referring to FIG. 1, the absorbent core 18 is configured to store bodilyfluids discharged during use. The absorbent core 18 may be manufacturedin a wide variety of sizes and shapes, and may be profiled to havedifferent thickness, hydrophilic gradients, superabsorbent gradients,densities, or average basis weights at different x-y-directionalpositions across the face of the sanitary napkin 10. As shown in FIGS.2A and 2B, the absorbent core comprises a fluid distribution layer 20and a storage layer 22. The fluid distribution layer is configured totransfer the received fluid both downwardly and laterally, and generallyhas a higher permeability than the storage layer.

Fluid Distribution Layer

The fluid distribution layer is configured to acquire fluids from thetopsheet and store the fluid until such time that it can be absorbed bythe fluid storage layer. It is important that liquid held in the fluiddistribution layer does not transfer back to the topsheet (rewet). Thefluid distribution layer may have the same or similar shape and size asthe topsheet and overall absorbent article, or it may be smaller. Ingeneral, a well-functioning fluid distribution layer contributesconsiderably to the comfort experienced by a user and, as such, aims atbalancing the trade-off between the speed with which fluid is acquiredby the fluid distribution layer, the possibility of rewet and the levelof comfort provided to a user.

The fluid distribution layer has a structure that enables it to receiveand draw liquid from the topsheet, to hold the liquid and to preventrewet (e.g., through a topsheet), while still allowing the liquid to bedrawn out by the fluid storage layer. To address this, the fluiddistribution layer may comprise two or more sub-layers 34, 36, 42 havingdiffering properties. In this respect, it has been found that to drawliquid down and away from the topsheet, the fluid distribution layerneeds to have a certain permeability—that can be provided with agenerally open structure formed from fibers making up the fluiddistribution layers. However, the present inventors have realised thatproviding a wholly open structure can result in problems of rewet duringuse and, or it may lack the capillary action required to draw liquidaway from the topsheet in the first place.

The fluid distribution layer has a first body facing surface 38 and asecond garment facing surface 40 and is formed of two or more sub-layershaving different material properties. The first sub-layer 34 forms or isadjacent to the body facing surface of the fluid distribution layer(proximal to the topsheet). One or more additional sub-layers may beprovided. For example, a second sub-layer 36 is provided that forms oris adjacent to the garment facing surface of the fluid distributionlayer. Alternatively, a third sub-layer 42 (shown in FIG. 2B) could beprovided adjacent the garment facing surface of the fluid distributionlayer, in which case the second sub-layer is positioned between thefirst and third sub-layer. The ratio of fibers in the differentsub-layers may be different, but once integrated, the sub-layers formone heterogeneous structure that cannot be easily separated.

To ensure rapid acquisition of fluid but minimal rewet, it is necessaryfor the first sub-layer to be able to quickly draw liquid down from thetopsheet and to allow the liquid to pass through to the second (or more)sub-layer that is further away from the topsheet. The first sub-layershould also be capable of quickly recovering form to ensure that theuser does not experience a long period of discomfort as a result of thefluid distribution layer having become wet. To ensure the liquid is thenheld away from the topsheet, the second or subsequent sub-layers arerequired to continue to draw liquid away from the topsheet and firstsub-layer, but to hold the liquid until such time as it is absorbed bythe storage layer.

Sub-layers of the fluid distribution layer may be formed of acombination of pulp fibers and/or cross-linked cellulose fibers and/orbicomponent binder fibers and, dependent on the manufacturing process,optionally dispersion binder. The first sub-layer, located on thebody-facing side of the fluid distribution layer, has a more open, i.e.,less dense and more permeable, structure than the second or subsequentlayers. Thus, it is possible for the first sub-layer to quickly drawliquid into the absorbent core. The first sub-layer may comprisecrosslinked cellulose fibers or a combination of multi-component fibersand crosslinked cellulose fibers and/or pulp fibers. Where the firstsub-layer contains only fibers (e.g. crosslinked cellulose orcrosslinked cellulose and pulp fibers), the second and/or subsequentlayers of the fluid distribution layer will comprise multi-componentfibers. The presence of multi-component fibers in any part of the fluiddistribution layer helps to ensure integrity of the fluid distributionlayer as, upon heating, the multicomponent fibers form a self-adheringstructure.

Use of crosslinked fibers or multi-component binder fibers incombination with crosslinked or pulp fibers in the first sub-layer hasbeen found to provide an open structure that allows quick acquisition ofliquid from the top sheet and has good recovery properties after liquidhas been removed from the fluid distribution layer by the fluid storagelayer. Both factors contribute significantly to comfort experienced by auser both in wet and dry conditions.

The first sub-layer may comprise from 50%, 60%, 70%, 80% or 90% byweight of the first sub-layer of a first amount of crosslinked cellulosefibers, optionally comprising additional multicomponent binder fibers,pulp fibers and/or dispersion binders. Alternatively, the firstsub-layer may comprise from 25% to 75%, 30% to 70% or 40% to 60% byweight of the first sub-layer of multicomponent fibers, together withcross-linked or pulp fibers and optionally dispersion binders.Alternatively, the first sub-layer may comprise from 25% to 100% byweight of the first sub-layer of crosslinked cellulose fibers or pulpfibers and from 0% to 75% by weight of the first sub-layer ofmulticomponent fibers or 40% to 100% by weight of the first sub-layer ofcrosslinked cellulose fibers or pulp fibers and from 0% to 60% by weightof the first sub-layer of multicomponent fibers. Preferably, the secondsub-layer may comprise a second amount of crosslinked cellulose fibersand/or multicomponent binder fibers where the % by weight of the secondsub-layer of the second amount is less than the first amount. Subsequentsub-layers may comprise the same or less % by weight of each subsequentsub-layer than the second amount of crosslinked and/or multicomponentbinder fibers. Preferably, the second and any subsequent sub-layerscomprise less than 70%, 60%, 50%, 30% or 10% by weight of the respectivesub-layer of cross-linked and/or multicomponent binder fibers as thefirst amount of cross-linked cellulose or multicomponent fibers in thefirst sub-layer.

Preferably, the first sub-layer comprises from 50% to 70% by weight ofthe first sub-layer of multicomponent binder fibers and from 30% to 50%by weight of the first sub-layer of crosslinked cellulose or pulp fibersand the second sub-layer comprises less than 20% by weight of the secondsub-layer of multicomponent binder and/or crosslinked cellulose fibers.In an alternative preferred embodiment, the first sub-layer comprisesfrom 25% to 100% of crosslinked cellulose fibers and from 5% to 75% byweight of the first sub-layer of multicomponent fibers and the secondsub-layer comprises less than 20% by weight of the second sub-layer ofmulticomponent binder and/or crosslinked cellulose fibers.

Without being bound by theory, the multicomponent binder fibers enhancestructural integrity of the fluid distribution layer while alsoproviding for a more open structure. The crosslinked cellulose fibersprovide liquid storage capability and provide a springy open structurethat enables quick recovery of the fluid distribution layer to enablereadiness for multiple assaults. Use of a first amount of multicomponentfibers or crosslinked cellulose fibers in the first sub-layer that isgreater than the second or subsequent amounts of multicomponent fibersand/or crosslinked cellulose fibers in the second or subsequentsub-layers has been found to provide the benefits discussed above.However, in an embodiment, the first sub-layer comprises a first amountof cross-linked fibers and multicomponent fibers.

The second and subsequent sub-layers comprise treated or untreated pulpand may additionally comprise multicomponent binder fibers, crosslinkedcellulose fibers or a dispersion binder, such as latex, or a combinationthereof. Preferably, the second and subsequent sub-layers comprise nomore than 50% by weight of the total fluid distribution layer ofcrosslinked cellulose fibers or multicomponent binder fibers.

Preferably, the first sub-layer has a % weight of the fluid distributionlayer of between 20% to 60%. If the first sub-layer has a % weight ofless than 20%, it is expected that the acquisition of time of liquidsfrom the topsheet will increase and comfort levels will decrease. Bycontrast, if the weight ratio of first sub-layer to second or subsequentsub-layers is too great, then the open structure of the first sub-layermay not provide sufficient suction force to draw liquids away fromliquid receiving surface and/or the topsheet.

Multicomponent binder fibers can be formed, for example, by polyethyleneand polypropylene, polyethylene/polyethylene terephthalate, metallocenePP with PET core, and can have any configuration known in the art suchas for example core-sheath, star, fiber eccentric, fiber concentric,side by side and a mixture thereof.

Often, an absorbent article, when being worn, is exposed to a certainpressure exerted by the wearer, which potentially decreases the voidspace in the fluid distribution member. Having good permeability andsufficient void space available is important for good liquiddistribution and transport. It is further believed that the bi-componentfibers and cross-linked cellulose fibers described above are suitable tomaintain sufficient void volume even when a fluid distribution layer isexposed to pressure.

The remaining fibers may be selected from natural, regenerated andsynthetic fibers. In order to improve wettability, it is preferred thatat least 90% weight of the fibers (or in some embodiments, 100% wt) arehydrophilic or are hydrophilically treated (e.g., with a surfactant) soas to exhibit hydrophilic properties. The multicomponent binder fibersmay also be treated to exhibit hydrophilic properties.

Examples of fibers suitable for use in the fluid distribution layer (inaddition to the multicomponent binder fibers) are synthetic orregenerated fibers selected from PET, polyethylene, polypropylene,nylon, rayon, pulp, polylactic acid and mixtures thereof.

In addition to the materials described above, the fluid distributionlayer can comprise a wide variety of liquid-absorbent materials commonlyused in disposable absorbent articles. Non-limiting examples ofliquid-absorbent materials suitable for use include comminuted wood pulpwhich is generally referred to as airfelt or pulp; creped cellulosewadding; chemically stiffened, modified, or cross-linked cellulosefibers, cotton fibers; meltblown polymers including co-form; syntheticfibers including crimped polyester fibers; capillary channel fibers;absorbent foams; absorbent sponges; synthetic staple fibers.

The fluid distribution layer may be formed as a unitarystructure—meaning that although it may be formed by several sub-layersthat have distinct properties and/or compositions from one another, theyare somehow intermixed at the boundary region so that, instead of adefinite boundary between sub-layers, it would be possible to identify aregion where the different sub-layers transition one into the other.Such a unitary structure is typically built by forming the varioussub-layers one on top of the other in a continuous manner, for exampleusing air laid or wet laid deposition. Typically, there is no adhesiveused between the sub-layers of the unitary material. However, in somecases, adhesives and/or binders can be present although typically in alower amount that in multilayer materials formed by separate layers.

In an embodiment, the fluid distribution layer may comprise a fibrousnonwoven layer comprising fibers having an average length from 25 mm to200 mm, 50 mm to 175 mm or 75 mm to 125 mm. In some embodiments, theaverage fiber size in dtex can be selected so as to be in the range offrom 0.5 dtex to 15 dtex, 1 dtex to 12.5 dtex, 3 dtex to 10 dtex or 5dtex to 7.5 dtex. The average fiber length is measured according to ASTMmethod D5103-07 and the average size in dtex according to the ASTMmethod D1577-07. The nonwoven layer forming the unitary fluiddistribution layer can have a basis weight of from 10 g/m² to 50 g/m²,15 g/m² to 40 g/m², 20 g/m² to 30 g/m² and a thickness from 0.2 mm to 5mm, 0.5 mm to 4 mm, or 1 mm to 3 mm and can be selected fromneedlepunched, hydroentangled, air through bonded, spunbonded, cardedresin bonded, and melt blown nonwoven materials. Air through cardednonwovens are in some cases preferred because this consolidationtechnology can result in materials having a good z-direction compressionresistance, and good capillarity even at low basis weight (thus allowingto manufacture thinner and lower cost absorbent elements).

The nonwoven layer of the fluid distribution layer can be manufacturedfrom an assortment of suitable fiber types that produce the desiredmechanical performance and fluid handling performance. In someembodiments, an air through bonded carded nonwoven may be formed from acombination of stiffening fibers. The stiffening fibers, for example,can form about 20% to about 40%, by weight, of the air through cardedfiber nonwoven. In other embodiments, the stiffening fibers can formabout 100%, by weight, of the nonwoven.

The stiffening fibers can be polyethylene terephthalate (PET) fibers, orother suitable non-cellulosic fibers known in the art. The PET fiberscan have any suitable structure or shape. For example, the PET fiberscan be round or have other shapes, such as spiral, scalloped oval,trilobal, scalloped ribbon, and so forth. Further, the PET fibers can besolid, hollow or multi-hollow. In some embodiments of the carded fibernonwoven, the stiffening fibers may be fibers made of hollow/spiral PET.Other suitable examples of stiffening fibers includepolyester/co-extruded polyester fibers. The stiffening fibers may bemulticomponent binder fibers, where individual fibers are provided fromdifferent materials, usually a first and a second polymeric material.The two materials may be chemically different (hence the fibers arechemically heterogeneous) or they may differ only in their physicalproperties while being chemically identical (hence the fibers arechemically homogeneous). The stiffening fibers may also be a blend ofmulticomponent fibers with polyester fibers.

With specific reference to multicomponent fibers comprised of apolypropylene/polyethylene fiber composition, in a cross-sectional viewof a fiber, the material with a higher softening temperature can providethe central part (i.e., the core) of the fiber. The fiber core typicallyis responsible for the bicomponent fiber's ability to transmit forcesand have a certain rigidity or otherwise provide structures withresiliency. The outer coating on the fiber core (i.e., the sheath) ofthe fiber can have a lower melting point and may be used to facilitatethermally bonding of substrates comprising such fibers. In oneembodiment, a polypropylene core is provided with a polyethylene coatingon the outside, such that about 50%, by weight, of the fiber material ispolypropylene and 50%, by weight, of the fiber material is polyethylene.Other quantitative amounts can of course be selected. For example,bicomponent fibers can have a composition from about 30% to about 70%,by weight, polyethylene, while others have about 35% to about 65%, byweight polyethylene. In some embodiments, bicomponent fibers can have acomposition from about 40% to about 60% or about 45% to about 55%, byweight, polyethylene.

In a preferred embodiment of the present invention, the unitarystructure of the fluid distribution layer may be formed as an airlaidmaterial where the at least two sublayers forming it are deposited insubsequent steps on a single airlaid line directly onto the wire carrierand then latex applied to the body facing and garment facing surfaces toensure proper binding and reduce dustiness.

In each of the processes described above, the sub-layers are formed onan air laid machinery having several forming heads (in general one foreach sub layer or that two forming heads could deposit the samecomposition, thereby forming a single sub-layer) and wherein eachforming head lays down a specific combination of materials in a givenset of conditions. In this process a first forming head forms a firstair laid layer, then a second forming head forms a second air laidsub-layer on top of the first sub-layer. The process goes on until thedesired series of sub-layers is obtained. Typically, during thedeposition of an air laid layer or sub-layer the composition of thematerials (e.g., % of multi-component fibers) deposited by each forminghead is constant, however it is possible to envision embodiments wherethe composition of the materials of each forming head varies. Thisallows generating a variation of composition and properties of thematerial along its z axis in a single layer or sub-layer (-z profiling).In the case where more forming heads are present it is possible toconduct gentle compression steps between the passage from one forminghead to another, preferably without intermixing of the adjacentsub-layers.

When the deposition of the air laid fluid distribution layer is completethe resulting material may be compressed to compact it (e.g., viacalendering). In case multicomponent binder fibers are present, thematerial can be thermally treated at a temperature above the softeningtemperature of a bonding component of the multicomponent binder fibersand below the softening point of a structural component in themulticomponent binder fibers so that the binder fibers can bind amongsub-layers. The fluid distribution layer may additionally be embossedwhich may be beneficial for the wet integrity of the fluid distributionlayer and to increase its density. The resulting sheet of material canthen be cut if necessary in the appropriate size and used within theabsorbent core of an absorbent article or combined with another layer toform an absorbent core.

The thickness of the fluid distribution layer may be from 0.25 mm to 5mm, 0.75 mm to 3.5 mm, 1 mm to 2.5 mm or 1.5 mm to 2 mm. The thicknessis determined by the need to balance fluid handling and protection andcomfort of the article. For example, if the fluid distribution layer istoo thin, it may not be effective to prevent rewet of the article; ifthe fluid distribution layer is too thick, it may add unnecessary bulkto the absorbent article. In general, for use in menstrual articles, thefluid distribution layer may have a thickness of between 1.8 mm and 4.0mm; between 2.25 mm and 3.75 mm; between 2.5 mm and 3.5 mm; or between2.5 mm and 3.0 mm including any values within these ranges and anyranges created thereby. For use in light weight menstrual articles, thefluid distribution layer may have a thickness of from from 0.6 mm to 1.8mm. When used in articles aiming at handling urine, such as diapers oradult incontinence pads, the fluid distribution layer may have athickness of between 0.2 mm and 5.0 mm; between 2.25 mm and 3.75 mm;between 2.5 mm and 3.5 mm; or between 2.5 mm and 3.0 mm.

Fluid Storage Layer

The absorbent core further comprises a storage layer 22 containing superabsorbent polymers (SAP), such as absorbent gelling materials (AGM) orsuper absorbent foam materials. The storage layer may comprise from 50%,60%, 70%, 80% or 90% by weight of the storage layer of super absorbentpolymers. The amount of super absorbent polymer material in the fluidstorage layer enables the storage layer to draw liquid from the fluiddistribution layer, even when the two layers are structurally distinct(i.e., there are no fibers crossing between the layers that wouldotherwise allow easy transfer of liquid). The fluid storage layerfurther provides a secure place for exudates to be held when in use.

Absorbent gelling materials (AGM), are typically used in finelydispersed form, e.g. typically in particulate or fiberized form, inorder to improve their absorption and retention characteristics. AGMtypically comprises water insoluble, water swellable, hydrogel formingcrosslinked absorbent polymers which are capable of absorbing largequantities of liquids and of retaining such absorbed liquids undermoderate pressure. Absorbent gelling materials can be incorporated inabsorbent articles, typically in the absorbent core, in different ways;for example, absorbent gelling materials in particulate form can bedispersed among the fibres of one or more of the fibrous layerscomprised in the core, or rather localized in a more concentratedarrangement between fibrous layers so that one or more of the layersmaking up the core comprise a reduced amount of fibrous materials and/orare essentially made of AGM.

Other examples of AGM according suitable for the present invention areporous super absorbents such as those described in WO 2010118272 A1.

Other examples of SAP suitable for the present invention are foamsderived from the polymerization of High Internal Phase Emulsions(Water-in-oil or oil in water emulsions having a high ratio of dispersedaqueous phase to continuous oil phase), also referred to as “HIPEfoams”. These are formed by polymerizing a High Internal Phase Emulsioncomprising an oil phase having monomer, cross-linking agent, emulsifier,photo initiator, and an aqueous phase. Examples of HIPE foams aredescribed in: U.S. Pat. Nos. 5,500,451, 5,817,704, 5,856,366, 5,869,171,6,369,121, 6,376,565, 6,525,106 and WO 2011081987.

Such superabsorbent HIPE foams are typically cured into layers but canalso be used in comminuted form as particles or crumbles which can beapplied dispersed into storage layers alone or in combination withabsorbent or non absorbent fibers essentially in a similar way to AGMparticles.

Absorbent articles according to the present invention may comprise anyof the SAPs mentioned above or a mixture thereof.

In some embodiments, portions of the storage layer 22 of the absorbentcore can be formed only of SAP, or can be formed of SAP dispersed in asuitable carrier such as cellulose fibers in the form of fluff orstiffened fibers. One example of a non-limiting storage layer comprisesAGM particles that may be laminated between liquid permeable layers,such as conventional paper tissue layer (for example, having a basisweight of between 15 g/m² to 20 g/m²), or hydrophilic nonwovenmaterials, such as those conventionally used for topsheets.

The storage layer may further comprise materials, such as crepedcellulose wadding, fluffed cellulose fibers, Rayon fibers, wood pulpfibers also known as airfelt, and synthetic fibers, including celluloseacetate, polyvinyl fluoride, polyvinylidene chloride, acrylics (such asORLON), polyvinyl acetate, non-soluble polyvinyl alcohol, polyethylene,polypropylene, polyamides (such as nylon), polyesters, bicomponentfibers, tricomponent fibers, mixtures thereof and the like can also beused in the storage layer. The storage layer may also include fillermaterials, such as PERLITE, diatomaceous earth, VERMICULITE, or othersuitable materials that lower rewet problems.

The storage layer may have SAP in a uniform distribution or in anon-uniform distribution. The SAP may be in the form of channels,pockets, stripes, criss-cross patterns, swirls, dots, or any otherpattern, either two or three dimensional. Suitable storage layers may bemade in-line during the manufacturing process for absorbent articleswith high production speeds of more than 300 m/min or even more than 500m/min. However, it is often preferred (for process simplicity) that thestorage layer materials are provided in a web or sheet form, such thatthey may be provided pre-formed to a converting unit for making theabsorbent articles. In a preferred execution, materials for the storagelayer are roll-stock materials, i.e., may be supplied in the form of aweb—i.e., essentially a continuous roll or spool. This can reduce thecomplexity of the manufacturing process by eliminating a complex coreforming process step and by reducing additional dust generation.

The Absorbent Core

The absorbent core has a first, upper or body-facing surface and asecond, lower or garment facing surface. The body facing surface may beadjacent to the topsheet or may be adjacent an additional layer providedbetween the topsheet and absorbent core. The garment facing surface ofthe absorbent core may be adjacent the backsheet. The absorbent corecomprises at least a fluid distribution layer that is adjacent to orforms the body facing surface and a fluid storage layer that is adjacentto or forms the garment facing surface. The fluid distribution layer andfluid storage layer are preferably formed as distinct layers that areput together to form the absorbent core. The fluid distribution layerand fluid storage layer may be adhered together by any known means.Given the separate structure and function of the fluid distributionlayer and storage layer of the present invention, it is possible toprovide a more tailor made absorbent article having a large fluiddistribution layer proximal a user's skin and a smaller storage layerdistal to the user's skin. The fluid distribution layer is typicallysoft and cushiony so can provide a great degree of comfort to the user,whereas the storage layer is typically stiffer and denser. There aremany variations of how the storage layer may be arranged, but in oneexample, the storage layer may be positioned directly in the crotchregion—this could be for liquid absorption and comfort reasons.

Thus, the storage layer may have a smaller overall surface area than thefluid distribution layer. For example, the storage layer may have asmaller cross direction width, for example extending up to 90% of thewidth of the fluid distribution layer. Alternatively, the storage layermay have a smaller machine direction length, for example, extending upto 90% of the length of the fluid distribution layer.

In use, the fluid distribution layer will first receive exudates fromthe body and the capillary flow resulting from the arrangement ofdifferent materials of the sub-layers of the fluid distribution layer,will quickly draw the liquid away from the body facing surface of theabsorbent article. Due to the high absorption capacity and power of thestorage layer, liquid will be drawn from the fluid distribution layerinto the storage layer, thus leaving the fluid distribution layer readyto receive subsequent assaults of exudates. In this respect, the SAPpresent in the storage layers provide a strong suction force to drawliquid out of the fluid distribution layer.

Furthermore, the sub-layers of the fluid distribution layer have beenselected and designed such that once the exudates have been drawn intothe storage layer, the fluid distribution layer reverts to a cushionyform that is comfortable for the user.

Test Methods

To demonstrate the benefits of the absorbent article of the presentinvention, exemplary articles incorporating absorbent cores have beenevaluated using the following test methods:

The measurements for thickness provided herein were obtained usingWorldwide Strategic Partners (WSP) Test Method 120.1 (05) using a 0.25kPa load.

The measurements for basis weight provided herein were obtained usingWorldwide Strategic Partners (WSP) Test Method 130.1.

The measurements for Multiple Strike-Through time and End rewet wereobtained by the method described below.

Photographic representations of Stain Perception Measurement Method wereobtained by the method described below.

Unless otherwise specified, all tests described herein were conducted onsamples conditioned at a temperature of 73° F.±4° F. (about 23° C.±2.2°C.) and a relative humidity of 50%±4% for 2 hours prior to the test.

Multiple Strike-Through & End Rewet

The Multiple Strike-through methods measures the time required forrepetitive acquisition of Artificial Menstrual Fluid (AMF) loads onto atest sample. The required time is an indication of the sample's abilityto absorb fluid after repeated fluid loads under a given pressure.Acquisition time is measured by using a strike-through plate and anelectronic circuit interval timer. The time required for the absorbentarticle to acquire a dose of AMF is recorded. All measurements areperformed in a laboratory maintained at 23° C.±2 C.° and 50%±2% relativehumidity.

The rewet method measures the amount of fluid emerging through arepeated wetted topsheet from a wet underlying absorbent structure tocause removable wetness on the topsheet surface. Rewet serves as anestimate of how skin, being in contact with an absorbent structure,could be wetted 5 minutes after the last gush. This method works forfluid amounts of 3×3 ml to simulate an average load on pads. This fluidamounts reflect approx. 90% tile of product loading and the resultsreflect competitive product performance.

Test liquid AMF preparation: The Artificial Menstrual Fluid (AMF) iscomposed of a mixture of defibrinated sheep blood, a phosphate bufferedsaline solution and a mucous component. The AMF is prepared according tothe procedure described below such that it has a kinematic viscositybetween 7.15 to 8.65 centistokes at 23° C.

Viscosity on the AMF is performed using a low viscosity rotaryviscometer (a suitable instrument is the Cannon LV-2020 RotaryViscometer with UL adapter, Cannon Instrument Co., State College, Pa.,or equivalent). The appropriate size spindle for the viscosity range isselected, and the instrument is operated and calibrated as per themanufacturer. Measurements are taken at 23° C.±1 C.° and at 60 rpm.Results are reported to the nearest 0.01 centistokes.

Reagents needed for the AMF preparation include: defibrinated sheepblood with a packed cell volume of 38% or greater (collected understerile conditions, available from Cleveland Scientific, Inc., Bath,Ohio., or equivalent), gastric mucin with a viscosity target of 3-4centistokes when prepared as a 2% aqueous solution (crude form,available from Sterilized American Laboratories, Inc., Omaha, Nebr., orequivalent), 10% on a volume per volume basis lactic acid aqueoussolution, 10% on a volume per volume basis potassium hydroxide aqueoussolution, sodium phosphate dibasic anhydrous (reagent grade), sodiumchloride (reagent grade), sodium phosphate monobasic monohydrate(reagent grade) and distilled water, each available from VWRInternational or equivalent source.

The phosphate buffered saline solution consists of two individuallyprepared solutions (Solution A and Solution B). To prepare 1 litre ofSolution A, add 1.38±0.005 g of sodium phosphate monobasic monohydrateand 8.50±0.005 g of sodium chloride to a 1000 mL volumetric flask andadd distilled water to volume. Mix thoroughly. To prepare 1 litre ofSolution B, add 1.42±0.005 g of sodium phosphate dibasic anhydrous and8.50±0.005 g of sodium chloride to a 1000 mL volumetric flask and adddistilled water to volume. Mix thoroughly. To prepare the phosphatebuffered saline solution, add 450±10 mL of Solution B to a 1000 mLbeaker and stir at low speed on a stir plate. Insert a calibrated pHprobe (accurate to 0.1 units) into the beaker of Solution B and addenough Solution A, while stirring, to bring the pH to 7.2±0.1.

The mucous component is a mixture of the phosphate buffered salinesolution, potassium hydroxide aqueous solution, gastric mucin and lacticacid aqueous solution. The amount of gastric mucin added to the mucouscomponent directly affects the final viscosity of the prepared AMF. Todetermine the amount of gastric mucin needed to achieve AMF within thetarget viscosity range (7.15-8.65 centistokes at 23° C.) prepare 3batches of AMF with varying amounts of gastric mucin in the mucouscomponent, and then interpolate the exact amount needed from aconcentration versus viscosity curve with a least squares linear fitthrough the three points. A successful range of gastric mucin is usuallybetween 38 to 50 grams.

To prepare about 500 ml of the mucous component, add 460±10 mL of thepreviously prepared phosphate buffered saline solution and 7.5±0.5 mL ofthe 10% weight per volume potassium hydroxide aqueous solution to a 1000mL heavy duty glass beaker. Place this beaker onto a stirring hot plateand while stirring, bring the temperature to 45° C.±5 C°. Weigh thepre-determined amount of gastric mucin (±0.50 g) and slowly sprinkle it,without clumping, into the previously prepared liquid that has beenbrought to 45° C. Cover the beaker and continue mixing. Over a period of15 minutes bring the temperature of this mixture to above 50° C. but notto exceed 80° C. Continue heating with gentle stirring for 2.5 hourswhile maintaining this temperature range. After the 2.5 hours haselapsed, remove the beaker from the hot plate and cool to below 40° C.Next add 1.8±0.2 ml of the 10% v/v lactic acid aqueous solution and mixthoroughly. Autoclave the mucous component mixture at 121° C. for 15minutes and allow 5 minutes for cool down. Remove the mixture of mucouscomponent from the autoclave and stir until the temperature reaches 23°C.±1 C°.

Allow the temperature of the sheep blood and mucous component to come to23° C.±1 C°. Using a 500 ml graduated cylinder, measure the volume ofthe entire batch of the previously prepared mucous component and add itto a 1200 ml beaker. Add an equal volume of sheep blood to the beakerand mix thoroughly. Using the viscosity method previously described,ensure the viscosity of the AMF is between 7.15-8.65 centistokes. Ifnot, the batch is disposed and another batch is made adjusting themucous component as appropriate.

The qualified AMF should be refrigerated at 4° C. unless intended forimmediate use. AMF may be stored in an air-tight container at 4° C. forup to 48 hours after preparation. Prior to testing, the AMF must bebrought to 23° C.±1 C°. Any unused portion is discarded after testing iscomplete.

Referring to FIGS. 3, 4A, 4B, 5A and 5B, the strikethrough plate 9001 isconstructed of Plexiglas with an overall dimension of 10.2 cm long by10.2 cm wide by 3.2 cm tall. A longitudinal channel 9007 runs the lengthof the plate is 13 mm deep, 28 mm wide at the top plane of the plate,with lateral walls that slope downward at 65° to a 15 mm wide base. Acentral test fluid well 9009 is 26 mm long, 24 mm deep, 38 mm wide atthe top plane of the plate with lateral walls that slope downward at 65°to a 15 mm wide base. At the base of the test fluid well 9009, there isan “H” shaped test fluid reservoir 9003 open to the bottom of the platefor the fluid to be introduced onto the underlying article. The testfluid reservoir 9003 has an overall length of 25 mm, width of 15 mm, anddepth of 8 mm. The longitudinal legs of the reservoir are 4 mm wide withrounded ends. The central strut has a radius of 3 mm and houses theopposing electrodes 6 mm apart. The lateral sides of the reservoir bowoutward at a radius of 14 mm bounded by the overall width of 15 mm. Twowells 9002 (80.5 mm long×24.5 mm wide×25 mm deep) located outboard ofthe lateral channel, are filled with lead shot to adjust the overallmass of the plate to provide a constraining pressure of 0.25 psi (17.6gf/cm2) to the test area. Electrodes 9004 are embedded in the plate9001, connecting the exterior banana jacks 9006 to the inside wall ofthe fluid reservoir 9003. A circuit interval timer is plugged into thejacks 9006, and monitors the impedance between the two electrodes 9004,and measures the time from introduction of the AMF into reservoir 9003until the AMF drains from the reservoir. The timer has a resolution of0.01 sec.

The test samples may be finished test products that are removed from allpackaging using care not to press down or pull on the products whilehandling. No attempt is made to smooth out wrinkles. The test samplesare conditioned at 23° C.±2 C.° and 50%±2% relative humidity for atleast 2 hours prior to testing. Alternatively, the test samples may beprepared by positioning an absorbent core underneath a conventionaltopsheet, such as a 25 g/m2 spun highloft nonwoven made ofmulticomponent binder fibers, e.g., formed from 2.2 dtex, 4mm long PEsheath and PET core, or 1.7 dtex PE sheath/PP core, bicomponent fibers.For purposes of the tests described herein, all final test samples usedhad the same overall dimensions of length (216 mm) and width (62 mm).

The required mass of the strikethrough plate must be calculated for thespecific dimensions of the test article such that a confining pressureof 1.72 kPa is applied. Determine the longitudinal and lateral midpointof the test sample's absorbent core. Measure and record the lateralwidth of the core to the nearest 0.1 cm. The required mass of thestrikethrough plate is calculated as the core width multiplied bystrikethrough plate length (10.2 cm) multiplied byl7.6 g/cm2 andrecorded to the nearest 0.1 g. Add lead shot to the plate to achieve thecalculated mass.

Connect the electronic circuit interval timer to the strikethrough plate9001 and zero the timer. Place the test product onto a flat, horizontalsurface with the body side facing up. Gently place the strikethroughplate 9001 onto the center of the test sample ensuring that the “H”shaped reservoir 9003 is centered over the test area.

Using a mechanical pipette, accurately pipette 3.00 mL±0.05 mL of AMFinto the test fluid reservoir 9003. The fluid is dispensed, withoutsplashing, along the molded lip of the bottom of the reservoir 9003within a period of 3 seconds or less. After the fluid has been acquired,record the acquisition time to the nearest 0.01 second. Thoroughly cleanthe electrodes 9004 before each test.

Wait five minutes after the end of the fluid acquisition, withoutremoving the plate from the sample. Repeat the measurement twice withthe same fluid amount with 5 minutes waiting time between themeasurements to reach a total of three repetitive gushes. Write downeach single acquisition time.

In like fashion, a total of five (5) replicates samples are tested foreach test product to be evaluated. Report the Acquisition Time (sec) asthe arithmetic mean of the replicates to the nearest 0.01 sec.

Procedure End Rewet after Multiple Strike-Through:

After the last of three gushes of fluid has been acquired wait another 5minutes. Prepare seven sheets of filter paper during this time (filterpaper—Schleicher & Schuell N° 597, diameter 150 mm, #10311812), ensuringthat the filter paper is stored under the same climatic conditionsduring the test. For each test sample a new stack of filter paper isneeded. Take the filter paper by the edge, avoid touching the center.After the 5 minutes waiting time remove the plate and the additionalelements from the sample.

Put the test sample under the hydraulic lowering device and place thetorn filter paper stack on the test sample. Start the hydraulic loweringdevice to place the weight (1 psi) and wait 15 seconds.

After the hydraulic lowering device removes the weight, take the stackof filter paper and weigh it to the nearest 0.01 g. Record the weight.Discard used filter paper and tested products. Repeat the procedure forn=5 replicates.

Thickness

The thickness of a layer of the absorbent element structure according tothe present invention, as well as of a combinations of layers, forexample of an entire absorbent element structure, can be measured withany available method known to the skilled person under the selectedconfining pressure of 0.25±0.01 psi. For example, the INDA standard testmethod WSP 120.1 (05) can be used, wherein for the “Thickness testinggage” described under section 5.1, the “applied force”, section 5.1.e,is set at 0.25±0.01 psi, and the “Readability”, section 5.1.f, has to be0.01 mm.

Stain Perception Measurement Method

Stain perception is measured by the size of a fluid stain visible on anabsorbent article. Artificial menstrual fluid (AMF), as describedherein, is dosed onto the surface of an article and is photographedunder controlled conditions. The photographic image is then analyzedusing image analysis software to obtain measurements of the size of theresulting visible stain. All measurements are performed at constanttemperature (23° C.±2 C.° and relative humidity (50%±2%).

The absorbent article sample is cut at the center of the absorbentarticle with an area of 40×40mm and along with a calibrated ruler(traceable to NIST or equivalent) is laid horizontally flat on a matteblack background inside a light box that provides stable uniformlighting evenly across the entire base of the light box.

A suitable light box is the Sanoto MK50 (Sanoto, Guangdong, China), orequivalent, which provide an illumination of 5500 LUX at a colortemperature of 5500K. A Digital Single-Lens Reflex (DSLR) camera withmanual setting controls (e.g. a Nikon D40X available from Nikon Inc.,Tokyo, Japan, or equivalent) is mounted directly above an opening in thetop of the light box so that the entire article and ruler are visiblewithin the camera's field of view.

Using a standard 18% gray card (e.g., Munsell 18% Reflectance (Gray)Neutral Patch/Kodak Gray Card R-27, available from X-Rite; Grand Rapids,Mich., or equivalent) the camera's white balance is custom set for thelighting conditions inside the light box. The camera's manual settingsare set so that the image is properly exposed such that there is nosignal clipping in any of the color channels. Suitable settings might bean aperture setting of f/11, an ISO setting of 400, and a shutter speedsetting of 1/400 sec. At a focal length of 35 mm the camera is mountedapproximately 14 inches above the article. The image is properlyfocused, captured, and saved as a JPEG file. The resulting image mustcontain the entire article and distance scale at a minimum resolution of15 pixels/mm.

Sample absorbent articles are conditioned at 23° C.±2 C.° and 50%±2%relative humidity for 2 hours prior to testing. Place a sample articleflat, with the top sheet of the product facing upward, on the mattesurface within the light box along with the ruler. Using a mechanicalpipette held approximately 19 mm above the article surface, 2.0 mL 0.05mL of AMF is slowly and steadily loaded onto the center of the articleover a 60 second time period. Images are captured at 60 seconds afterthe loading.

TABLE 1 Fluid Distribution Layer Table 1: Formulation of Test SamplesOption Number 1 2 3 Option Name Inventive Inventive Sample 1 Sample 2Control gsm % gsm % gsm % Topsheet (NW PP) 25 25 25 Formulation of FluidDistribution Layer (% by weight of fluid distribution layer) FirstSub-layer 60 40 43.3 28.87 50.8 33.87 Latex (Wacker Airflex 2.5 1.7 2.51.7 192) Untreated Pulp (WY 22.5 15 38.7 25.8 NB416) Multicomponentfibers 37.5 25 15 10 9.6 6.4 (including NW carrier layer comprisingmulticomponent fibers where applicable) (2.2 dtex 4 mm PE/PET) Crosslinked cellulose 25.8 17.2 fibers Second Sub-layer 90 60 106.7 71.7399.2 66.13 Untreated Pulp (WY 81.5 54.3 92.2 61.5 NB416) Treated Pulp(GP4722) 77.5 51.7 Multicomponent fibers 6 4 12 8 19.2 12.8 Latex(Wacker Airflex 2.5 1.7 2.5 1.7 2.5 1.7 192) Total 150 100 150 100 150100 Formulation of Fluid Storage Layer Cellulose Tissue 35 35 35(Sofidel) AGM (Sayiya 35 35 35 Transform ex BASF) Backsheet (Polymeric12 12 12 Film)

Each sample additionally has the same non-woven topsheet and the same 12gsm polymeric film backsheet. The non-woven topsheet is a 25 g/m² spunhigh loft non-woven made of polypropylene (PP) fibers with 2% meltadditives on the bottom layer.

Note: Table 1 shows the different composition of the differentsub-layers of the fluid distribution layer. All % s are by weight of thefluid distribution layer. As described above, the non-woven carrierlayer may be formed of 50% to 100% of multicomponent binder fibers.Inventive sample 1 is formed with a non-woven carrier, whereas inventivesample 2 is formed by air-laying the fibers directly onto the carrierwire and subsequently applying latex to bind them. When calculating the% weight by individual sub-layers above, it can be seen that the controlfeatures an overall homogenous structure with approximately the same %of multicomponent fibers throughout. By comparison, inventive samples 1and 2 comprise a greater % of either cross-linked cellulose ormulticomponent fibers in the first sub-layer compared with the secondsub-layer.

TABLE 2 Multiple Strike-Through and End Rewet measurements Sample IS 1IS 2 Control Basis Weight (gsm) 150 150 150 1st Acquisition Time (sec)21 18 27 2nd Acquisition Time (sec) 50 48 75 3rd Acquisition Time (sec)89 81 133 End Rewet (g) 0.72 0.62 1.03

As can be seen above, the acquisition time for Inventive Samples 1 and 2is considerably lower than for the Control, even after multiple insults.Furthermore, the end rewet weight is less for Inventive Samples 1 and 2than the control. This can also be seen for the fluid distribution layerwhen considered alone—as shown in FIGS. 6A, 6B and 6C.

FIGS. 6A and 6B show the final stain size on the top surfaces of,respectively, the topsheet 100 and fluid distribution layer 102 forInventive Samples 1 (FIG. 6A) and Inventive Samples 2 (FIG. 6B). FIG. 6Cshows the final stain size on the top surfaces of, respective, thetopsheet 104 and fluid distribution layer 106 of the control. As canclearly be seen from these photographs, the stain size is significantlysmaller and less intense for Inventive Samples 1 and 2 vs the control.

-   A. An absorbent article, comprising:    -   a) a topsheet;    -   b) a backsheet; and    -   c) an absorbent core, the absorbent core comprising a fluid        distribution layer adjacent the topsheet, the fluid distribution        layer being formed of two or more sub-layers comprising:        -   i) a first sub-layer proximal to the topsheet, wherein the            first sub-layer comprises a first amount of multiple            component binder fibers or crosslinked cellulose fibers, or            a combination thereof;        -   ii) a second and/or subsequent sub-layer distal from the            topsheet, wherein the second and/or subsequent sub-layer            comprises treated or untreated pulp and a second amount of            multiple component binder fibers, crosslinked cellulose            fibers, or a combination thereof, wherein the % by weight of            the first sub-layer of the first amount of multicomponent            binder fibers and/or crosslinked cellulose fibers is greater            than the % by weight of the second and/or subsequent            sub-layers of the second amount of multicomponent binder            fibers and/or crosslinked cellulose fibers; and    -   d) a fluid storage layer between the fluid distribution layer        and the backsheet, wherein the fluid storage layer comprises at        least 50% by weight of the fluid storage layer of a super        absorbent polymer.-   B. An absorbent article of paragraph B, wherein the first sub-layer    further comprises treated or untreated pulp.-   C. An absorbent article as described in paragraph A or paragraph B,    wherein the fluid distribution layer comprises between 20% to 60% of    the first sub-layer by % weight of the fluid distribution layer.-   D. An absorbent article as described in any of paragraphs A to C,    wherein the first sub-layer comprises between 2% and 30% by weight    of the fluid distribution layer of multicomponent binder fibers or    crosslinked cellulose fibers.-   E. An absorbent article as described in any of paragraphs A to D,    wherein the fluid distribution layer comprises one or more    additional sub-layers adjacent the second sub-layer and distal to    the topsheet, wherein the one or more additional sub-layers comprise    the same or less % by weight of the fluid distribution layer of    multicomponent binder fibers or crosslinked cellulose fibers.-   F. An absorbent article as described in any of paragraphs A to E,    wherein the surface area of the fluid storage layer is less than the    surface area of the fluid distribution layer.-   G. An absorbent article as described in any of paragraphs A to F,    wherein the first sub-layer of the fluid distribution layer    comprises a non-woven layer that forms the first surface of the    fluid distribution layer.-   H. An absorbent article as described in any of paragraphs A to G,    wherein the fluid distribution layer comprises dispersion binder.-   I. An absorbent article as described in any of paragraphs A to H,    wherein the first sub-layer of the fluid distribution layer    comprises untreated or treated pulp fibers, crosslinked cellulose    fibers and multicomponent binder fibers.-   J. An absorbent article as described in any of paragraphs A to I,    wherein the fluid distribution layer is substantially free of super    absorbent polymers.-   K. An absorbent article as described in any of paragraphs A to J,    wherein said storage layer comprises superabsorbent polymers    selected from the group consisting of absorbent gelling material    (AGM) or absorbent foam.-   L. An absorbent article as described in any of paragraphs A to K,    wherein the first sub-layer comprises from 50% to 70% by weight of    the first sub-layer of multicomponent binder fibers and from 30% to    50% by weight of the first sub-layer of crosslinked cellulose or    pulp fibers and the second sub-layer comprises less than 20% by    weight of the second sub-layer of multicomponent binder and/or    crosslinked cellulose fibers.-   M. An absorbent article as described in any of paragraphs A to K,    wherein the first sub-layer comprises from 25% to 100% of    crosslinked cellulose fibers and from 5% to 75% by weight of the    first sub-layer of multicomponent fibers and the second sub-layer    comprises less than 20% by weight of the second sub-layer of    multicomponent binder and/or crosslinked cellulose fibers.

This application claims the benefit of EP Application No. 18172398.2,filed on May 15, 2018, the entireties of which are all incorporated byreference herein.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application and any patent application or patent to which thisapplication claims priority or benefit thereof, is hereby incorporatedherein by reference in its entirety unless expressly excluded orotherwise limited. The citation of any document is not an admission thatit is prior art with respect to any invention disclosed or claimedherein or that it alone, or in any combination with any other referenceor references, teaches, suggests or discloses any such invention.Further, to the extent that any meaning or definition of a term in thisdocument conflicts with any meaning or definition of the same term in adocument incorporated by reference, the meaning or definition assignedto that term in this document shall govern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. An absorbent article, comprising: a) a topsheet;b) a backsheet; and c) an absorbent core, the absorbent core comprisinga fluid distribution layer adjacent the topsheet, the fluid distributionlayer being formed of two or more sub-layers comprising: i) a firstsub-layer proximal to the topsheet, wherein the first sub-layercomprises a first amount of multiple component binder fibers orcrosslinked cellulose fibers, or a combination thereof; ii) a secondsub-layer distal from the topsheet, wherein the second sub-layercomprises treated or untreated pulp and a second amount of multiplecomponent binder fibers, crosslinked cellulose fibers, or a combinationthereof, wherein the % by weight of the first sub-layer of the firstamount of multicomponent binder fibers and/or crosslinked cellulosefibers is greater than the % by weight of the second sub-layer of thesecond amount of multicomponent binder fibers and/or crosslinkedcellulose fibers; and iii) a fluid storage layer between the fluiddistribution layer and the backsheet, wherein the fluid storage layercomprises at least 50% by weight of the fluid storage layer of a superabsorbent polymer.
 2. An absorbent article as claimed in claim 1,wherein the first sub-layer further comprises treated or untreated pulp.3. An absorbent article as claimed in claim 1, wherein the fluiddistribution layer comprises between 20% to 60% of the first sub-layerby % weight of the fluid distribution layer.
 4. An absorbent article asclaimed in claim 1, wherein the first sub-layer comprises between 2% and30% by weight of the fluid distribution layer of multicomponent binderfibers or crosslinked cellulose fibers.
 5. An absorbent article asclaimed in claim 1, wherein the fluid distribution layer comprises oneor more additional sub-layers adjacent the second sub-layer and distalto the topsheet, wherein the one or more additional sub-layers comprisethe same or less % by weight of the fluid distribution layer ofmulticomponent binder fibers or crosslinked cellulose fibers as thesecond amount of multicomponent binder fibers or crosslinked cellulosefibers by weight of the second sub-layer.
 6. An absorbent article asclaimed in claim 1, wherein the surface area of the fluid storage layeris less than the surface area of the fluid distribution layer.
 7. Anabsorbent article as claimed in claim 1, wherein the first sub-layer ofthe fluid distribution layer comprises a non-woven layer that forms thefirst surface of the fluid distribution layer.
 8. An absorbent articleas claimed in claim 1, wherein the fluid distribution layer comprisesdispersion binder.
 9. An absorbent article as claimed in claim 1,wherein the first sub-layer of the fluid distribution layer comprisesuntreated or treated pulp fibers, crosslinked cellulose fibers andmulticomponent binder fibers.
 10. An absorbent article as claimed inclaim 1, wherein the fluid distribution layer is substantially free ofsuper absorbent polymers.
 11. An absorbent article as claimed in claim1, wherein the fluid storage layer comprises superabsorbent polymersselected from the group consisting of absorbent gelling material orabsorbent foam.
 12. An absorbent article as claimed in claim 1, whereinthe first sub-layer comprises from 50% to 70% by weight of the firstsub-layer of multicomponent binder fibers and from 30% to 50% by weightof the first sub-layer of crosslinked cellulose or pulp fibers and thesecond sub-layer comprises less than 20% by weight of the secondsub-layer of multicomponent binder and/or crosslinked cellulose fibers.13. An absorbent article as claimed in claim 1, wherein the firstsub-layer comprises from 25% to 100% of crosslinked cellulose fibers andfrom 5% to 75% by weight of the first sub-layer of multicomponent fibersand the second sub-layer comprises less than 20% by weight of the secondsub-layer of multicomponent binder and/or crosslinked cellulose fibers.